1. Field of the Invention
The invention relates to a method and a device for controlling the heating of glow plugs in a diesel engine as are used to bring the glow plugs to a predetermined set point temperature at which the engine can be started.
2. Description of Related Art
The publication MTZ 10/2000 “Das elektronisch gesteuerte Glühsystem ISS für Dieselmotoren” [The electronically controlled ISS glow system for diesel engines] discloses a method for controlling the heating of glow plugs in a diesel engine. The glow command or glow requirement is issued after engine control initialization has been completed and after the temperature of the engine elements has been determined by way of the engine control system and subsequent successful establishment of communication between the engine control system and the glow control device.
For controlling the heating of the glow plugs of a diesel engine, it is important to know the thermal state of the glow plugs, fast-start glow plugs, in particular, for example, the residual temperature of the glow plugs after previous heating during repeated start and to include it in the following control. The thermal state of the glow plugs can be implemented to date however in the glow plug control system only from experiential values. To consider the residual temperature of the glow plug, knowledge of the entire history is necessary, requiring non-volatile memories and a time basis, in case data have to be included prior to resetting.
Measuring the glow plug temperature via the glow plug resistance is eliminated as a possibility of determining the glow plug temperature based on tolerances of the glow plugs with respect to their resistance course because of the real existing tolerances and the variable dynamic behavior. Calibrating the glow plugs is also not conceivable, as mass-produced components are involved here.